Generally, it is well known that a light emitting device using a light emitting element is compact and excellent in power efficiency and emits bright colors. The light emitting element used for the light emitting device is a semiconductor device. Therefore, the light emitting element is excellent in an initial drive performance in addition to almost free from blowout, and resistant to vibrations and repetitions of ON/OFF switching. Since the light emitting element has excellent characteristics as described above, a light emitting device using the light emitting element such as a light emitting diode (LED) and a laser diode (LD) is used for various kinds of light sources.    Patent literature 1: Japanese Patent Laid-open Publication No. 2005-259972    Patent literature 2: Japanese Patent Laid-open Publication No. 2001-177160    Patent literature 3: Japanese Patent Laid-open Publication No. H11-45958    Patent literature 4: Japanese Patent Laid-open Publication No. 2006-156704    Patent literature 5: Japanese Patent Laid-open Publication No. 2005-294736
Here, FIG. 10 is a side cross sectional view showing a conventional light emitting device 100 according to the Japanese Patent Laid-open Publication No. 2005-259972 or the Japanese Patent Laid-open Publication No. 2001-177160.
The conventional light emitting device 100 shown in FIG. 10 includes a light emitting element 101, a mounting lead frame 102 for mounting the light emitting element 101, a wiring lead frame 103 to be connected to the light emitting element 101 through a lead wire, and a resin mold body 104 covering a most part of each lead frame. The resin mold body 104 has, for example, a rectangular outer shape in plan view, and is provided with a concave portion 105 having a circular truncated cone shape which becomes narrower toward downward at approximately the center of the resin mold body 104. The mounting lead frame 102 is set on a bottom surface of the concave portion 105, and the light emitting element 101 is placed on an upper surface of the mounting lead frame 102. In addition, a resin 108 is disposed in the concave portion 105 as a light emitting portion.
As described above, since the light emitting portion is formed by filling the resin 108 in the concave portion 105 which is opened upward, a light emitted from the light emitting element 101 is uniformly reflected by the bottom surface and side surface of the concave portion 105. As a result, the light can be output from a light emitting surface side, on which the light emitting element 101 is placed, without polarizing.
Generally, the resin mold body 104 of the light emitting device 100 described above is integrally formed with the lead frames 102, 103. Here, FIG. 11 is a side cross sectional view showing a molding method of a conventional resin mold body (see Japanese Patent Laid-open Publication No. H11-45958).
A method for molding the resin mold body 104 is as follows. As shown in FIG. 11, the lead frames 102, 103 are set between an upper die 111 and a lower die 112, and a thermoplastic resin is injected and filled into a space 114 formed by the upper die 111 and the lower die 112 from an injection port 115. Then, the filled thermoplastic resin is cured to form the resin mold body 104 (hereinafter, this molding method is referred to as “molding method 1”).
The molding method 1 is characterized in that, by injecting a thermoplastic resin from the bottom center of the lower die 112, the resin is radially diffused, and thereby the resin is uniformly filled in every corner of the space 114. It is noted that a protruding portion 117 corresponding to the concave portion 105 is formed in the upper die 111.
However, there have been the following problems in the molding method 1. That is, in the molding method 1, since the injection port 115 is disposed at the bottom center of the resin mold body 104, a gate remain 106 is formed at the bottom center of the resin mold body 104 as shown in FIG. 10. The gate remain is a protrusion remaining on a resin mold body when the dies are opened and the resin mold body (gate), which is formed at the injection port portion when a thermoplastic resin is injected from the injection port, is cut off from the gate portion. If the gate remain 106 is formed at the bottom center of the resin mold body 104 as described above, this causes a problem (1) that a steady reflow bonding can not be ensured due to the cutting remain of the gate remain 106 when the reflow bonding to a wiring substrate 107 is conducted. In addition, if the gate remain 106 is formed at the bottom center of the resin mold body 104, this causes a problem (2) that when the lead frames 102, 103 are bended, the bending work is disturbed since a bending machine is caught in the cutting remain of the gate remain 106.
Further, in the molding method 1, since a thermoplastic resin is used, a fluidity of the resin is low, and as a result, the molding method 1 is inappropriate for molding the resin mold body 104 having a complex shape. In addition, there has been a problem (3) that a thermoplastic resin is poor in heat resistance and adhesiveness to the lead frame.
Therefore, a method for solving the problems described above has been considered, in which an injection port is disposed on an external wall portion 116 (see FIG. 11) of the upper die 111 or lower die 112 and a thermosetting resin is injected from the injection port to mold the resin mold body 104.
For example, an invention is described in the Japanese Patent Laid-open Publication No. 2006-156704 or the Japanese Patent Laid-open Publication No. 2005-294736, in which a thermosetting resin is injected into a space between the upper die and the lower die by a transfer molding. In the molding method described above, there is no specific description on the arrangement of injection port and an injecting direction. However, since a gate is disposed on an external side surface of the resin mold body, for example, by disposing the injection port on the external wall portion (see 116 in FIG. 11) of the upper die, the problem (1) and problem (2) can be solved. In addition, since a thermosetting resin is excellent in fluidity, heat resistance, and adhesiveness to lead frames, the problem (3) can be solved (hereinafter, this molding method is referred to as “conventional method”).